In known apparatus, the receptor cells are filled with a pretedermined quantity of a sample liquid by filling each of the compartments from a pipette. When the rotor is subsequently spun, the liquid contained in the various compartments moves outwardly towards the associated receptor cells. However, the apparatus cannot work for long unattended, since it must be moved to under a pipette in order to refill its verious compartments.
Preferred embodiments of the present invention mitigate this drawback.